LED device

ABSTRACT

A LED device includes LED chips mounted on a substrate, a first fluorescent layer, a second fluorescent layer and a package housing. The LED chips emit a blue light. The first fluorescent layer has a first side facing to the LED chips for converting the blue light to a red light. The second fluorescent layer has a first side attached to a second side of the first fluorescent layer for converting the blue light to a red light emitted from a second side of the second fluorescent layer. The package housing holds the substrate and the first fluorescent layer.

RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 15/892,358.

FIELD OF THE INVENTION

The present invention is related to a LED (light emitted diode) deviceand more particularly related to a LED device using multiple types ofphosphor materials.

BACKGROUND

After years of hard working, LED products have been widely spread overthe world. At beginning, the cost of LED products is too high,preventing LED products to be popular. Nowadays, LED product price haslowered to an acceptable level.

However, it is always important to further find every aspect to improvesuch devices, particularly for such worldwide products related to humandaily life. Heat efficiency, color rendering index, and morecharacteristics need to consider when designing LED devices.

In the present invention, inventors look deeper into the LED basicstructure and finds several inventive points to further improve LEDdevice performance.

SUMMARY OF INVENTION

According to a first embodiment of the present invention, a LED deviceincludes a LED module, a first fluorescent layer, a second fluorescentlayer and a package housing. The LED module includes a first group ofLED chips and a second group of LED chips mounted on a substrate foremitting an original light of an original spectrum. For example, the LEDchips are mounted on the substrate using Surface Mounting Device (SMD),Chip Scale Packaging (CSP), flip chip packaging, chip on board (COB) orother packaging methods.

The first fluorescent layer faces to the first group of LED chips forconverting the original light to a first output light of a firstspectrum. The second fluorescent layer faces to the second group of LEDchips for converting the original light to a second output light of asecond spectrum.

The package housing has a shape for holding the substrate, the firstfluorescent layer and the second fluorescent layer. The first spectrumis partially overlapped with an excitation spectrum of the secondfluorescent layer. In other words, when the first output light isemitted into the second fluorescent layer, the first output light may befurther converted to a light of the second spectrum.

In one embodiment, the package housing has a first container and asecond container for placing the first fluorescent layer and the secondfluorescent layer respectively.

In another embodiment, the package housing has more than two containersfor placing the first fluorescent layers and the second fluorescentlayer arranged in interleaved manner. With such arrangement, the mixedlight may be more smooth.

In some embodiments, there is a separating component for preventing thefirst output light to emit into the second fluorescent layer.

In some embodiments, furthermore, the separating component has areflecting surface for reflecting and guiding the first output light toa predetermined direction. Therefore, for light emitted onto thereflecting surface, the light is redirected to a desired direction, e.g.top of the LED device or to other directions as predetermined lightdistribution.

In some embodiments, the package housing has multiple side walls forreflecting and directing the first output light and the second outputlight to predetermined directions.

In some embodiments, furthermore, the side walls have a convex or aconcave structure engaging the first fluorescent layer or the secondfluorescent layer. With such arrangement, the first fluorescent layerand the second fluorescent layer may have better reliability on fixingto the substrate.

Such convex structure or concave structure provides position limitingeffect when materials the fluorescent layers are attached on or intosuch structures. Particularly, when the fluorescent layers are in gelmode when installed, such fluorescent layer flow and fit the surface ofthe concave or convex structures, forming a well holding structure.

In some embodiment, the first fluorescent layer has a first convexsurface on top of the first fluorescent layer, the second fluorescentlayer has a second convex surface on top of the second fluorescentlayer.

In such design, the first convex surface and the second convex surfaceform lens guiding the first output light and the second output light formixing the first output light and the second output light. Light pathsmay be well optimized for different light devices by adjusting the curveratio, e.g. to form a condensed beam or a diversified light.

Except convex surface, in some other embodiments, the first fluorescentlayer may have a first concave surface on top of the first fluorescentlayer, and the second fluorescent layer has a second concave surface ontop of the second fluorescent layer.

In some embodiments, the first output light, the second light and theoriginal light not absorbed by the first fluorescent layer and thesecond fluorescent layer form an overall output spectrum of a whitelight.

Specifically, in some embodiments, the first fluorescent layer and thesecond fluorescent layer both comprise red phosphor material forgenerating 640-650 nm output light. In some other embodiments, the firstfluorescent layer and the second fluorescent layer both comprise redphosphor material for generating 628-635 nm output light.

Please be noted that red, blue or green phosphor refer to phosphormaterial for emitting red, blue or green light, instead of defining thecolor of the phosphor materials themselves.

In some embodiments, the original spectrum is substantiallycorresponding to a blue light, the first spectrum is substantiallycorresponding to a green light, and the second spectrum is substantiallycorresponding to a red light.

In some other embodiments, the original spectrum is substantiallycorresponding to a ultraviolet light, the first fluorescent layercomprises green phosphor material and blue phosphor material forgenerating a green light and a blue light, the second fluorescent layercomprises red phosphor material for generating a red light.

In some other embodiments, the original spectrum is substantiallycorresponding to a ultraviolet light, the first fluorescent layercomprises green phosphor material and red phosphor material forgenerating a green light and a red light, the second fluorescent layercomprises blue phosphor material for generating a blue light.

In some embodiments, the first fluorescent layer and the secondfluorescent layer have phosphor material, and the phosphor material haslarger density near bottom than top in the first fluorescent layer andthe second fluorescent layer. This increases better light efficacybecause the bottom part of the first and the second fluorescent layersare closer to the light source, thus increasing phosphor excitationefficiency.

In some embodiments, the second fluorescent layer has a larger area thanthe first fluorescent layer.

In some embodiments, the second group of LED chips have more LED chipsthan the first group of LED chips.

According to another embodiment of the present invention, a LED (lightemitted diode) device is provided. The LED device has a LED module, afirst fluorescent layer, a second fluorescent layer, and a packagehousing.

The LED module is mounted on a substrate for emitting a blue light.

The first fluorescent layer has a first side facing to the LED modulefor converting the blue light to a red light.

The second fluorescent layer has a first side attached to a second sideof the first fluorescent layer for converting the blue light to a redlight emitted from a second side of the second fluorescent layer.

The package housing holds the substrate and the first fluorescent layer.

With such design, the first fluorescent layer is between the secondfluorescent layer and the LED module. In other words, a blue lightemitted from the LED module firstly enters the first fluorescent layer,hitting certain phosphor material and generating corresponding redlight. In addition, some part of the blue light further moves to thesecond fluorescent layer to hit other phosphor material to generategreen light. With red light and green light, users may see a white lighteffect.

In some embodiments, the LED module has multiple LED chips emitting theblue light. The substrate has a first terminal area and a secondterminal area for mounting the multiple LED chips. For example, multipleLED chips are mounted on conductive plates used as the terminal areaswith surface mounting device (SMD) technology.

The first terminal area and the second terminal area are provided forrespectively connected to a positive terminal and a negative terminal ofa power source. The first terminal area may have different size as thesecond terminal area. For example, when there are more LED chips mountedon the first terminal area than on the second terminal area, the firstterminal area may have a larger size than the second terminal area toprovide better heat dissipation effect.

In some embodiments, the first fluorescent has red phosphor materialcontained in first silicone part, and the second fluorescent layer hasgreen phosphor material contained in a second silicone part. Please benoted that other materials in addition to silica gel, like resin, may beused for containing phosphor powder.

In addition, a part of the green light may excite the red phosphor ifthe green light hits the red phosphor. In other words, if the blue lightfirstly enters the second fluorescent layer, the blue light may firstlybe converted to green light. If such green light continues to move intothe first fluorescent layer, part or all of the green light may beconsumed and converted into red light. This may decrease the overallgreen light energy and decreases an overall CRI (color rendering index)of the LED device.

Therefore, it is beneficial to place the first fluorescent layer betweenthe second fluorescent layer and the LED module, for improving greenlight output and deceasing undesired consumption of the green lightoutput.

Inventors also find that there the volume ratio of phosphor material inthe first fluorescent layer and the second fluorescent layer may beadjusted to further improve different characteristics of the LED device.

In some cases, a first volume ratio of the red phosphor to the firstsilicone part is larger than a second volume ratio of the green phosphorto the second silicone part.

In some other cases, a first volume ratio of the red phosphor to thefirst silicone part is smaller than a second volume ratio of the greenphosphor to the second silicone part.

These embodiments provide different features and characteristics,suitable for making various LED products.

In some embodiments, a thickness of the first fluorescent layer islarger than a thickness of the second fluorescent layer.

In some other embodiments, a thickness of the first fluorescent layer issmaller than a thickness of the second fluorescent layer.

Such variations are found helpful for adjusting product characteristicof the LED device.

In addition, the first fluorescent layer may have better heat resistingfeature than the second fluorescent layer, when the first fluorescentlayer is placed closer to the LED module. In other words, designers mayplace phosphor material with less heat resisting characteristic as thesecond fluorescent layer.

In some embodiments, the package housing may have a bottom part fixed tothe substrate and the package housing has a surrounding wall extendedfrom the bottom part. The wall defines a containing space for holdingthe first fluorescent layer.

For example, the package housing has a hole for holding the substrateand four connecting walls forming a rectangular containing space. Thefirst fluorescent layer and sometimes the second fluorescent layer areplaced in the containing space.

There are several ways to design the second fluorescent layer.

In some embodiments, a second side of the second fluorescent layer has acurved surface. In other words, the top surface of the secondfluorescent layer may have a curve surface.

Specifically, an angle of edges of the first side and the second side ofthe second fluorescent layer would be less than 60 degrees. Such designmay increase overall product stability.

In some embodiments, the curve surface forms a convex lens, providingbetter optical characteristic for output light, by directing light todesired direction.

According to another embodiment of the present invention, a LED deviceincludes a LED module, a first fluorescent layer, and a secondfluorescent layer.

The LED module includes a plurality of LED components mounted on asubstrate for emitting an original light of an original spectrum.

The first fluorescent layer surrounds the plurality of LED componentsfor converting the original light to a first output light of a firstspectrum. The second fluorescent layer is stacked on the firstfluorescent layer for converting the original light not absorbed by thefirst fluorescent layer and entering the second fluorescent layer to asecond output light of a second spectrum. In addition, the secondspectrum is partially overlapped with an excitation spectrum of thesecond fluorescent layer.

In some embodiment, the LED device further includes a package housingfor holding the substrate and the first fluorescent layer. The substratehas a plurality of electrode pads. The plurality of LED components areattached to the plurality of electrode pads and electrically connectedwith wires. The electrode pads are connected to an external power sourceto drive the LED components to emit the original light.

In some embodiments, the LED components are LED semiconductor chipsmounted on the substrate using chip-on-board packaging.

In some other embodiments, the LED component is made with CSP (ChipScale Package). In addition, the LED device may include a packagehousing with reflecting walls for reflecting the original light, thefirst output light, the second output light to predetermined directions.On designing the angle of the reflecting walls, the second output lightis prevented to enter the first fluorescent layer to cause energy wasteand total output of the second output light.

In some other embodiments, the substrate is an elongated strip. Suchelongated strip with LED modules may be used for manufacturing variousbulbs emulating the shape of traditional bulbs. In addition, when thesubstrate is transparent, e.g. glass material, the LED device mayfurther have a third fluorescent layer attaching to a backside of theelongated strip for converting the original light passing through theelongated strip to a third output light of the first spectrum, and afourth fluorescent layer stacked on the third fluorescent layer forconverting the original light not absorbed by the third fluorescentlayer and entering the fourth fluorescent layer to a fourth output lightof the second spectrum.

In some other embodiments, the substrate is a flexible circuit boardsubstrate.

In some embodiments, the LED device may further have a side wall fixedto the substrate. The side wall has a convex structure or a concavestructure engaging the second fluorescent layer. Such convex structureand concave structure may also be used for fixing the first fluorescentlayer. This is particularly helpful when the first fluorescent layer andthe second fluorescent layer are heated to gel mode duringmanufacturing. It is difficult to control the surface temperature of thefluorescent layers to be attached together. With such structures, thefluorescent layers are fixed more reliably.

In some embodiments, the first fluorescent layer has a first convexsurface on top of the first fluorescent layer, the second fluorescentlayer has a second convex surface on top of the second fluorescentlayer. The first convex surface and the second convex surface may formone or more lens guiding the first output light and the second outputlight for mixing the first output light and the second output light.

In some other embodiments, the first fluorescent layer has a firstconcave surface on top of the first fluorescent layer, the secondfluorescent layer has a second concave surface on top of the secondfluorescent layer.

In some embodiments, there is a boundary surface between the firstfluorescent layer and the second fluorescent layer, and the boundarysurface is a convex surface facing to the LED module.

In some other embodiments, the boundary surface between the firstfluorescent layer and the second fluorescent layer is a concave surfacefacing to the LED module.

In some embodiments, the first output light, the second light and theoriginal light not absorbed by the first fluorescent layer and thesecond fluorescent layer form an overall output spectrum of a whitelight.

Furthermore, in some embodiments, the first fluorescent layer and thesecond fluorescent layer both include red phosphor material forgenerating 640-650 nm output light.

In some other embodiments, the first fluorescent layer and the secondfluorescent layer both include red phosphor material for generating628-635 nm output light.

In some embodiments, there is an intermediate part between the firstfluorescent layer and the second fluorescent layer. The intermediatepart includes mixed materials of the first fluorescent layer and thesecond fluorescent layer. The thickness of the intermediate part may beless than 10% of the total width of the first fluorescent layer and thesecond fluorescent layer. The intermediate part has a plurality of microconvex structures between the first fluorescent layer and the secondfluorescent layer. Such convex structures may form a plurality of microoptical lens for better distribute light paths.

In another embodiment according to the present invention, a LED deviceincludes a LED module, a first fluorescent layer and a secondfluorescent layer.

The LED module includes a plurality of LED components mounted on asubstrate for emitting an original light of an original spectrum. Thefirst fluorescent layer surrounds the plurality of LED components forconverting the original light to a first output light of a firstspectrum. The second fluorescent layer is stacked on the firstfluorescent layer for converting the original light not absorbed by thefirst fluorescent layer and entering the second fluorescent layer togenerate a second output light of a second spectrum.

The second spectrum is partially overlapped with an excitation spectrumof the first fluorescent layer. In addition, there is an intermediatepart between the first fluorescent layer and the second fluorescentlayer. The intermediate part includes mixed materials of the firstfluorescent layer and the second fluorescent layer. The intermediatepart has a plurality of micro convex structures between the firstfluorescent layer and the second fluorescent layer.

In some embodiments, the first fluorescent layer is a dome shape and thesecond fluorescent layer and the substrate surround the firstfluorescent layer.

In some embodiments, the LED device further includes a package housing,wherein the package housing and the substrate form a container forstoring the first fluorescent layer.

In some embodiments, the package housing has a surrounding side wallwith larger peripheral size at top than at bottom, e.g. like an invertedpyramid. Such structure further prevents unnecessary waste of the secondoutput light to be emitted into the first fluorescent layer.

In some embodiments, the package housing has a surrounding side wallwith a reflecting surface facing to the first fluorescent layer.

In some embodiments, a heat dissipation material, like powder mixed withmetal oxide or metal crystals, may bed mixed in the first fluorescentlayer.

In some embodiments, the original spectrum is substantiallycorresponding to a ultraviolet light. The second fluorescent layercontains green phosphor material and blue phosphor material forgenerating a green light and a blue light, the first fluorescent layercontains red phosphor material for generating a red light.

In some embodiments, the LED device may further include a thirdfluorescent layer containing blue phosphor material for generating bluelight spectrum. The second fluorescent layer may contain green phosphormaterial for generating a green light, and the first fluorescent layermay contain red phosphor material for generating a red light.

In some embodiments, the first fluorescent layer may contain redphosphor material and green phosphor material for generating a red lightand a green light and the second fluorescent layer may contain bluephosphor material for generating a blue light.

In some other embodiments, area of the second side of the secondfluorescent layer is smaller than area of the second side of the firstfluorescent layer. In other words, when being looked over a top view, apart of the second side of the first fluorescent layer is exposed anduncovered by the second fluorescent layer.

In such case, there is an embodiment to place the second fluorescent inthe middle place, which causes the second side of second fluorescentlayer being surrounded by the second side of the first fluorescent layerfrom a top view.

In some embodiments, the package housing has a ladder wall for engagingwith a peripheral part of the second fluorescent layer. In somemanufacturing procedures, the first fluorescent layer and the secondfluorescent layer are heated as gel mode to be filled into the packageholding. When the package holding has a ladder wall, the firstfluorescent layer may be filled in a first ladder while the secondfluorescent layer may be filled to in a second ladder upper than thefirst ladder in the ladder wall.

In some embodiments, the second side of the second fluorescent layerforms a flat surface.

In some other embodiments, the second side of second fluorescent layerforms a curve surface for different optical characteristic requirement.

In some embodiments, the second side of the second fluorescent layer mayhave multiple convex part corresponding to multiple underlying LED chipsof the LED module. It may be implemented by applying gel mode materialof the second fluorescent layer to the package for several timesrespectively to underlying LED chips. Because LED chips usually havecertain light emitting angle, it is helpful to maximize the lightconverting effect by placing more material of the second fluorescentlayer on top of corresponding LED chips, particularly when phosphormaterial is critical cost in LED devices.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a LED device embodiment.

FIG. 2 is a top view of FIG. 1.

FIG. 3. Illustrates a first fluorescent layer installed in a LED deviceembodiment.

FIG. 4 illustrates a top view of FIG. 3.

FIG. 5 illustrates a first way to add a second fluorescent layer.

FIG. 6 illustrates a top view of FIG. 5.

FIG. 7 illustrates another way to add a second fluorescent layer.

FIG. 8 illustrates a top view of FIG. 7.

FIG. 9 illustrates another way to add a second fluorescent layer.

FIG. 10 illustrates LED chips in an embodiment.

FIG. 11 illustrates another side view of a LED device embodiment.

FIG. 12 illustrates a top view of a LED device embodiment.

FIG. 13 illustrates a optical characteristic diagram of an experimentalresult.

FIG. 14 illustrates another optical characteristic diagram of anexperimental result.

FIG. 15A is a diagram illustrating fluorescent layer shapes of anembodiment.

FIG. 15B is a diagram illustrating fluorescent layer shapes of anotherembodiment.

FIG. 15C is a diagram illustrating fluorescent layer shapes of anotherembodiment.

FIG. 16A is a diagram illustrating fluorescent layer curve surfaces ofan embodiment.

FIG. 16B is a diagram illustrating fluorescent layer curve surfaces ofanother embodiment.

FIG. 17A illustrates an auxiliary fixing structure for fixing thefluorescent layer in an embodiment.

FIG. 17B illustrates an auxiliary fixing structure for fixing thefluorescent layer in another embodiment.

FIG. 18 illustrates an intermediate part between fluorescent layers.

FIG. 19A illustrates another embodiment of a LED device.

FIG. 19B illustrates another embodiment of a LED device.

FIG. 19C illustrates another embodiment of a LED device.

FIG. 20A illustrates another embodiment of a LED device.

FIG. 20B illustrates another embodiment of a LED device.

FIG. 21A illustrates another embodiment of a LED device.

FIG. 21B illustrates another embodiment of a LED device.

FIG. 21C illustrates another embodiment of a LED device.

FIG. 22A illustrates another embodiment of a LED device.

FIG. 22B illustrates another embodiment of a LED device.

FIG. 23A illustrates another embodiment of a LED device.

FIG. 23B illustrates another embodiment of a LED device.

FIG. 23C illustrates another embodiment of a LED device.

FIG. 24 illustrates another embodiment of a LED device.

FIG. 25 illustrates another embodiment of a LED device.

DETAILED DESCRIPTION

According to an embodiment of the present invention, a LED deviceincludes a LED module, a first fluorescent layer, a second fluorescentlayer and a package housing. The LED module includes a first group ofLED chips and a second group of LED chips mounted on a substrate foremitting an original light of an original spectrum. For example, the LEDchips are mounted on the substrate using Surface Mounting Device (SMD),Chip Scale Packaging (CSP), flip chip packaging, chip on board (COB) orother packaging methods.

The first fluorescent layer faces to the first group of LED chips forconverting the original light to a first output light of a firstspectrum. The second fluorescent layer faces to the second group of LEDchips for converting the original light to a second output light of asecond spectrum.

The package housing has a shape for holding the substrate, the firstfluorescent layer and the second fluorescent layer. The first spectrumis partially overlapped with an excitation spectrum of the secondfluorescent layer. In other words, when the first output light isemitted into the second fluorescent layer, the first output light may befurther converted to a light of the second spectrum.

In one embodiment, the package housing has a first container and asecond container for placing the first fluorescent layer and the secondfluorescent layer respectively.

In another embodiment, the package housing has more than two containersfor placing the first fluorescent layers and the second fluorescentlayer arranged in interleaved manner. With such arrangement, the mixedlight may be more smooth.

In some embodiments, there is a separating component for preventing thefirst output light to emit into the second fluorescent layer.

In some embodiments, furthermore, the separating component has areflecting surface for reflecting and guiding the first output light toa predetermined direction. Therefore, for light emitted onto thereflecting surface, the light is redirected to a desired direction, e.g.top of the LED device or to other directions as predetermined lightdistribution.

In some embodiments, the package housing has multiple side walls forreflecting and directing the first output light and the second outputlight to predetermined directions.

In some embodiments, furthermore, the side walls has a convex or aconcave structure engaging the first fluorescent layer or the secondfluorescent layer. With such arrangement, the first fluorescent layerand the second fluorescent layer may have better reliability on fixingto the substrate.

Such convex structure or concave structure provides position limitingeffect when materials the fluorescent layers are attached on or intosuch structures. Particularly, when the fluorescent layers are in gelmode when installed, such fluorescent layer flow and fit the surface ofthe concave or convex structures, forming a well holding structure.

In some embodiment, the first fluorescent layer has a first convexsurface on top of the first fluorescent layer, the second fluorescentlayer has a second convex surface on top of the second fluorescentlayer.

In such design, the first convex surface and the second convex surfaceform lens guiding the first output light and the second output light formixing the first output light and the second output light. Light pathsmay be well optimized for different light devices by adjusting the curveratio, e.g. to form a condensed beam or a diversified light.

Except convex surface, in some other embodiments, the first fluorescentlayer may have a first concave surface on top of the first fluorescentlayer, and the second fluorescent layer has a second concave surface ontop of the second fluorescent layer.

In some embodiments, the first output light, the second light and theoriginal light not absorbed by the first fluorescent layer and thesecond fluorescent layer form an overall output spectrum of a whitelight.

Specifically, in some embodiments, the first fluorescent layer and thesecond fluorescent layer both comprise red phosphor material forgenerating 640-650 nm output light. In some other embodiments, the firstfluorescent layer and the second fluorescent layer both comprise redphosphor material for generating 628-635 nm output light.

Please be noted that red, blue or green phosphor refer to phosphormaterial for emitting red, blue or green light, instead of defining thecolor of the phosphor materials themselves.

In some embodiments, the original spectrum is substantiallycorresponding to a blue light, the first spectrum is substantiallycorresponding to a green light, and the second spectrum is substantiallycorresponding to a red light.

In some other embodiments, the original spectrum is substantiallycorresponding to a ultraviolet light, the first fluorescent layercomprises green phosphor material and blue phosphor material forgenerating a green light and a blue light, the second fluorescent layercomprises red phosphor material for generating a red light.

In some other embodiments, the original spectrum is substantiallycorresponding to a ultraviolet light, the first fluorescent layercomprises green phosphor material and red phosphor material forgenerating a green light and a red light, the second fluorescent layercomprises blue phosphor material for generating a blue light.

In some embodiments, the first fluorescent layer and the secondfluorescent layer have phosphor material, and the phosphor material haslarger density near bottom than top in the first fluorescent layer andthe second fluorescent layer. This increases better light efficacybecause the bottom part of the first and the second fluorescent layersare closer to the light source, thus increasing phosphor excitationefficiency.

In some embodiments, the second fluorescent layer has a larger area thanthe first fluorescent layer.

In some embodiments, the second group of LED chips have more LED chipsthan the first group of LED chips.

According to another embodiment of the present invention, a LED deviceincludes a LED module, a first fluorescent layer, and a secondfluorescent layer.

The LED module includes a plurality of LED components mounted on asubstrate for emitting an original light of an original spectrum.

The first fluorescent layer surrounds the plurality of LED componentsfor converting the original light to a first output light of a firstspectrum. The second fluorescent layer is stacked on the firstfluorescent layer for converting the original light not absorbed by thefirst fluorescent layer and entering the second fluorescent layer to asecond output light of a second spectrum. In addition, the secondspectrum is partially overlapped with an excitation spectrum of thesecond fluorescent layer.

In some embodiment, the LED device further includes a package housingfor holding the substrate and the first fluorescent layer. The substratehas a plurality of electrode pads. The plurality of LED components areattached to the plurality of electrode pads and electrically connectedwith wires. The electrode pads are connected to an external power sourceto drive the LED components to emit the original light.

In some embodiments, the LED components are LED semiconductor chipsmounted on the substrate using chip-on-board packaging.

In some other embodiments, the LED component is made with CSP (ChipScale Package). In addition, the LED device may include a packagehousing with reflecting walls for reflecting the original light, thefirst output light, the second output light to predetermined directions.On designing the angle of the reflecting walls, the second output lightis prevented to enter the first fluorescent layer to cause energy wasteand total output of the second output light.

In some other embodiments, the substrate is an elongated strip. Suchelongated strip with LED modules may be used for manufacturing variousbulbs emulating the shape of traditional bulbs. In addition, when thesubstrate is transparent, e.g. glass material, the LED device mayfurther have a third fluorescent layer attaching to a backside of theelongated strip for converting the original light passing through theelongated strip to a third output light of the first spectrum, and afourth fluorescent layer stacked on the third fluorescent layer forconverting the original light not absorbed by the third fluorescentlayer and entering the fourth fluorescent layer to a fourth output lightof the second spectrum.

In some other embodiments, the substrate is a flexible circuit boardsubstrate.

In some embodiments, the LED device may further have a side wall fixedto the substrate. The side wall has a convex structure or a concavestructure engaging the second fluorescent layer. Such convex structureand concave structure may also be used for fixing the first fluorescentlayer. This is particularly helpful when the first fluorescent layer andthe second fluorescent layer are heated to gel mode duringmanufacturing. It is difficult to control the surface temperature of thefluorescent layers to be attached together. With such structures, thefluorescent layers are fixed more reliably.

In some embodiments, the first fluorescent layer has a first convexsurface on top of the first fluorescent layer, the second fluorescentlayer has a second convex surface on top of the second fluorescentlayer. The first convex surface and the second convex surface mayforming one or more lens guiding the first output light and the secondoutput light for mixing the first output light and the second outputlight.

In some other embodiments, the first fluorescent layer has a firstconcave surface on top of the first fluorescent layer, the secondfluorescent layer has a second concave surface on top of the secondfluorescent layer.

In some embodiments, there is a boundary surface between the firstfluorescent layer and the second fluorescent layer, and the boundarysurface is a convex surface facing to the LED module.

In some other embodiments, the boundary surface between the firstfluorescent layer and the second fluorescent layer is a concave surfacefacing to the LED module.

In some embodiments, the first output light, the second light and theoriginal light not absorbed by the first fluorescent layer and thesecond fluorescent layer form an overall output spectrum of a whitelight.

Furthermore, in some embodiments, the first fluorescent layer and thesecond fluorescent layer both include red phosphor material forgenerating 640-650 nm output light.

In some other embodiments, the first fluorescent layer and the secondfluorescent layer both include red phosphor material for generating628-635 nm output light.

In some embodiments, there is an intermediate part between the firstfluorescent layer and the second fluorescent layer. The intermediatepart includes mixed materials of the first fluorescent layer and thesecond fluorescent layer. The thickness of the intermediate part may beless than 10% of the total width of the first fluorescent layer and thesecond fluorescent layer. The intermediate part has a plurality of microconvex structures between the first fluorescent layer and the secondfluorescent layer. Such convex structures may form a plurality of microoptical lens for better distribute light paths.

The LED module includes a plurality of LED components mounted on asubstrate for emitting an original light of an original spectrum. Thefirst fluorescent layer surrounds the plurality of LED components forconverting the original light to a first output light of a firstspectrum. The second fluorescent layer is stacked on the firstfluorescent layer for converting the original light not absorbed by thefirst fluorescent layer and entering the second fluorescent layer togenerate a second output light of a second spectrum.

The second spectrum is partially overlapped with an excitation spectrumof the first fluorescent layer. In addition, there is an intermediatepart between the first fluorescent layer and the second fluorescentlayer. The intermediate part includes mixed materials of the firstfluorescent layer and the second fluorescent layer. The intermediatepart has a plurality of micro convex structures between the firstfluorescent layer and the second fluorescent layer.

In some embodiments, the first fluorescent layer is a dome shape and thesecond fluorescent layer and the substrate surround the firstfluorescent layer.

In some embodiments, the LED device further includes a package housing,wherein the package housing and the substrate form a container forstoring the first fluorescent layer.

In some embodiments, the package housing has a surrounding side wallwith larger peripheral size at top than at bottom, e.g. like an invertedpyramid. Such structure further prevents unnecessary waste of the secondoutput light to be emitted into the first fluorescent layer.

In some embodiments, the package housing has a surrounding side wallwith a reflecting surface facing to the first fluorescent layer.

In some embodiments, a heat dissipation material, like powder mixed withmetal oxide or metal crystals, may bed mixed in the first fluorescentlayer.

In some embodiments, the original spectrum is substantiallycorresponding to a ultraviolet light. The second fluorescent layercontains green phosphor material and blue phosphor material forgenerating a green light and a blue light, the first fluorescent layercontains red phosphor material for generating a red light.

In some embodiments, the LED device may further include a thirdfluorescent layer containing blue phosphor material for generating bluelight spectrum. The second fluorescent layer may contain green phosphormaterial for generating a green light, and the first fluorescent layermay contain red phosphor material for generating a red light.

In some embodiments, the first fluorescent layer may contain redphosphor material and green phosphor material for generating a red lightand a green light and the second fluorescent layer may contain bluephosphor material for generating a blue light.

According to another embodiment of the present invention, a LED (lightemitted diode) device is provided. The LED device has a LED module, afirst fluorescent layer, a second fluorescent layer, and a packagehousing.

The LED module is mounted on a substrate for emitting a blue light.

The first fluorescent layer has a first side facing to the LED modulefor converting the blue light to a red light.

The second fluorescent layer has a first side attached to a second sideof the first fluorescent layer for converting the blue light to a redlight emitted from a second side of the second fluorescent layer.

The package housing holds the substrate and the first fluorescent layer.

With such design, the first fluorescent layer is between the secondfluorescent layer and the LED module. In other words, a blue lightemitted from the LED module firstly enters the first fluorescent layer,hitting certain phosphor material and generating corresponding redlight. In addition, some part of the blue light further moves to thesecond fluorescent layer to hit other phosphor material to generategreen light. With red light and green light, users may see a white lighteffect.

In some embodiments, the LED module has multiple LED chips emitting theblue light. The substrate has a first terminal area and a secondterminal area for mounting the multiple LED chips. For example, multipleLED chips are mounted on conductive plates used as the terminal areaswith surface mounting device (SMD) technology.

The first terminal area and the second terminal area are provided forrespectively connected to a positive terminal and a negative terminal ofa power source. The first terminal area may have different size as thesecond terminal area. For example, when there are more LED chips mountedon the first terminal area than on the second terminal area, the firstterminal area may have a larger size than the second terminal area toprovide better heat dissipation effect.

In some embodiments, the first fluorescent has red phosphor materialcontained in first silicone part, and the second fluorescent layer hasgreen phosphor material contained in a second silicone part. Please benoted that other materials in addition to silica gel, like resin, may beused for containing phosphor powder.

In addition, a part of the green light may excite the red phosphor ifthe green light hits the red phosphor. In other words, if the blue lightfirstly enters the second fluorescent layer, the blue light may firstlybe converted to green light. If such green light continues to move intothe first fluorescent layer, part or all of the green light may beconsumed and converted into red light. This may decrease the overallgreen light energy and decreases an overall CRI (color rendering index)of the LED device.

Therefore, it is beneficial to place the first fluorescent layer betweenthe second fluorescent layer and the LED module, for improving greenlight output and deceasing undesired consumption of the green lightoutput.

Inventors also find that there the volume ratio of phosphor material inthe first fluorescent layer and the second fluorescent layer may beadjusted to further improve different characteristics of the LED device.

In some cases, a first volume ratio of the red phosphor to the firstsilicone part is larger than a second volume ratio of the green phosphorto the second silicone part.

In some other cases, a first volume ratio of the red phosphor to thefirst silicone part is smaller than a second volume ratio of the greenphosphor to the second silicone part.

The provide different features and characteristics, suitable for makingvarious LED products.

In some embodiments, a thickness of the first fluorescent layer islarger than a thickness of the second fluorescent layer.

In some other embodiments, a thickness of the first fluorescent layer issmaller than a thickness of the second fluorescent layer.

Such variations are found helpful for adjusting product characteristicof the LED device.

In addition, the first fluorescent layer may have better heat resistingfeature than the second fluorescent layer, when the first fluorescentlayer is placed closer to the LED module. In other words, designers mayplace phosphor material with less heat resisting characteristic as thesecond fluorescent layer.

In some embodiments, the package housing may have a bottom part fixed tothe substrate and the package housing has a surrounding wall extendedfrom the bottom part. The wall defines a containing space for holdingthe first fluorescent layer.

For example, the package housing has a hole for holding the substrateand four connecting walls forming a rectangular containing space. Thefirst fluorescent layer and sometimes the second fluorescent layer areplaced in the containing space.

There are several ways to design the second fluorescent layer.

In some embodiments, a second side of the second fluorescent layer has acurved surface. In other words, the top surface of the secondfluorescent layer may have a curve surface.

Specifically, an angle of edges of the first side and the second side ofthe second fluorescent layer would be less than 60 degrees. Such designmay increase overall product stability.

In some embodiments, the curve surface forms a convex lens, providingbetter optical characteristic for output light, by directing light todesired direction.

In some other embodiments, area of the second side of the secondfluorescent layer is smaller than area of the second side of the firstfluorescent layer. In other words, when being looked over a top view, apart of the second side of the first fluorescent layer is exposed anduncovered by the second fluorescent layer.

In such case, there is an embodiment to place the second fluorescent inthe middle place, which causes the second side of second fluorescentlayer being surrounded by the second side of the first fluorescent layerfrom a top view.

In some embodiments, the package housing has a ladder wall for engagingwith a peripheral part of the second fluorescent layer. In somemanufacturing procedures, the first fluorescent layer and the secondfluorescent layer are heated as gel mode to be filled into the packageholding. When the package holding has a ladder wall, the firstfluorescent layer may be filled in a first ladder while the secondfluorescent layer may be filled to in a second ladder upper than thefirst ladder in the ladder wall.

In some embodiments, the second side of the second fluorescent layerforms a flat surface.

In some other embodiments, the second side of second fluorescent layerforms a curve surface for different optical characteristic requirement.

In some embodiments, the second side of the second fluorescent layer mayhave multiple convex part corresponding to multiple underlying LED chipsof the LED module. It may be implemented by applying gel mode materialof the second fluorescent layer to the package for several timesrespectively to underlying LED chips. Because LED chips usually havecertain light emitting angle, it is helpful to maximize the lightconverting effect by placing more material of the second fluorescentlayer on top of corresponding LED chips, particularly when phosphormaterial is critical cost in LED devices.

Please refer to FIG. 1 to FIG. 6, illustrating a LED device embodiment.

The LED device has LED chips 1 and a bracket 2 for fixing the LED chips1. The LED bracket 2 contains a substrate 21 and four side walls 22 as apackage housing. The substrate 21 and the side walls 22 form acontaining space 23.

A first terminal area 211 and a second terminal area 212 are disposed onthe substrate. The LED chips 1 are placed in the containing space 23 andmounted on surface of the first terminal area 211 and the secondterminal area 212, e.g. via surface mounting device (SMD) technology.The LED chips 1 may be electrically connected in series or in othercombination. The first terminal area 211 and the second terminal 212 arefurther electrically connected to a power source to supply electricityto the LED chips 1.

A first fluorescent layer 31 is disposed for covering the LED chips 1. Asecond fluorescent layer 32 is on top of the first fluorescent layer 31.The wave length of emitted light of the first fluorescent layer 31 islonger than the wave length of emitted light of the second fluorescentlayer 32 when a blue light or an ultraviolet light is respectivelyemitted into the first fluorescent layer 31 and the second fluorescentlayer 32. For example, the first fluorescent layer emits red light whenblue light enters the first fluorescent layer 31, and the secondfluorescent layer emits green light when blue light enters the secondfluorescent layer 32.

In addition, the first fluorescent layer 31 may be made by mixing redphosphor in a silicone material, and the second fluorescent layer 32 maybe made by mixing green phosphor in a silicone material.

The LED chips 1 may be LED chips emitting blue light of wavelengthswithin range 380 nm to 470 nm. The green light emitted from the secondfluorescent layer 31 may be within range 500 nm to 560 nm. The red lightemitted from the first fluorescent layer 32 may be within 600 nm to 670nm.

Some blue light is not absorbed by either the first fluorescent layer 31or the second fluorescent layer 32. Therefore, in some embodiment, theoverall output light includes blue light, red light and green light,which together form a white light.

With such design, green light is not consumed by red phosphor materialand further improves CRI (color rendering index) and overall luminousefficacy.

Please be noted that the embodiment is only for explaining the inventiveconcept, instead of limiting the inventive scope. Other variations maybe made by persons of ordinary skilled in the art based on disclosure ofthis specification.

The bracket 2 may be SMD bracket made of PCT material, a mixture of CHDM(1,4-Cyclohexanedimethanol) and DMT (Terephthalic acid dimethyl ester).

Please refer to FIG. 5 and FIG. 6. In one embodiment, the firstfluorescent layer 31 is disposed in the containing space 23. The topsurface of the second side of the first fluorescent layer 31 is alignedwith the top surface of the side walls 22.

The first side of the second fluorescent layer 32 is placed on top ofthe first fluorescent layer 31. The size of the second side of thesecond fluorescent layer 32 is smaller than the size of the second sideof the first fluorescent layer 31. Therefore, part of the firstfluorescent layer 31 is exposed and uncovered by the second fluorescentlayer 32.

Please refer to FIG. 7 and FIG. 8, which illustrate another way to addthe second fluorescent layer.

In this embodiment, the first fluorescent layer 31 is placed in thecontaining space 23. The top surface of the first fluorescent layer 31is aligned with the top surface of the side walls 22. The secondfluorescent layer 32 is placed upon the first fluorescent layer 31.

In this embodiment, the second side of the second fluorescent layer 32has a curve surface. The angle between the first side and the secondside of the second fluorescent layer 32 is smaller than 60 degrees.

Please refer to FIG. 9 to FIG. 12.

In this embodiment, the side walls 22 have a ladder structure 221 fordividing the containing space 23 to a first containing space 231 and asecond containing space 232.

The area of the second containing space 232 is larger than the area ofthe first containing space 231. The first fluorescent layer 31 is placedin the first containing space 231 and the second fluorescent layer 32 isplaced in the second containing space 232.

Please refer to FIG. 13 and FIG. 14, which illustrate experimentalresults of such design.

FIG. 13 illustrate a conventional LED optical characteristic, while FIG.14 illustrates optical characteristic of an example of the invention. Itis clearly seen that the green light is well improved, which mayincrease overall CRI and luminous efficacy. Meanwhile, blue light isdecreased to protect human eyes.

Please refer to FIG. 15A, FIG. 15B and FIG. 15C, which illustrate threedifferent way to arrange the fluorescent layers.

In FIG. 15A, a first fluorescent layer 502 surrounds a LED module 503. Asecond fluorescent layer 501 is stacked on the first fluorescent layer502. A package housing 504 is used for providing a container for thefirst fluorescent layer 502.

In FIG. 15B, similar to FIG. 15A, a LED module 512 is surrounded by asecond fluorescent layer 512. A second fluorescent layer 511 is stackedon the first fluorescent layer 511.

In FIG. 15C, similar to FIG. 15B, an additional exposure of the firstfluorescent layer 515 is arranged, instead of covering the firstfluorescent layer 512 completely.

The intermediate surface between the first fluorescent layer 502 and thesecond fluorescent layer 501 is a convex surface, which may be used as alens for guiding light to desired direction. For example, to adjustlight beam angle, or mixing light of different colors.

The top surfaces of the first fluorescent layer and the secondfluorescent layer may be concave lens or concave lens, for differentoptical requirements.

Please refer to FIG. 16A and FIG. 16B.

In FIG. 16A, a LED module 614 is surrounded by a first fluorescent layer612. A second fluorescent layer 611 is stacked on the first fluorescentlayer 612. A package housing 613 provides a container for storing thefirst fluorescent layer 612.

In FIG. 16B, similarly, a LED module 624 is surrounded by a firstfluorescent layer 622. A second fluorescent layer 621 is stacked on thefirst fluorescent layer 622. A package housing 623 provides a containerfor storing the first fluorescent layer 622.

As mentioned before, the curve surface combination may have variousconfiguration to optimize light paths in corresponding light apparatusdesigns.

Please refer to FIG. 17A and FIG. 17B.

In FIG. 17A and FIG. 17B, a convex structure 711 and a concave structure712 are respectively disposed for fixing the top fluorescent layer morereliably. Usually, the fluorescent layers are inserted to the packagehousing in gel mode after being heated.

It is not easy to control cooling timing, while attachment betweenfluorescent layers depend on status between adjacent fluorescent layers.With such designs, fluorescent layers in gel or liquid mode may fill orhook the concave structure 712 or the convex structure to better fix thefluorescent layers more firmly.

Please refer to FIG. 18.

In FIG. 18, an intermediate part 811 exists between a first fluorescentlayer 813 and a second fluorescent layer 814. The intermediate part 811contains materials of both the first fluorescent layer 813 and thesecond fluorescent layer 814. For example, the first fluorescent layer813 may contain red phosphor and the second fluorescent layer 814 maycontain green phosphor. Both red and green phosphor exist in theintermediate part 811, which makes the overall light transmission betterfitting to design needs.

In addition, the intermediate surface 813 between the first fluorescentlayer 813 and the second fluorescent layer 814 may have a plurality ofmicro convex structures, serving as micro optical lens for guiding lighttransmission to better fit design requirements.

The thickness of the intermediate part 811 is less than 10% of the totalthickness of the first fluorescent layer 813 and the second fluorescentlayer 814.

Please refer to FIG. 19A, FIG. 19B and FIG. 19C.

In FIG. 19A, a LED device has three fluorescent layers. The firstfluorescent layer 913 may contain red phosphor material. The secondfluorescent layer 912 may contain green phosphor material and the thirdfluorescent layer 911 may contain blue phosphor material.

In FIG. 19B, a LED device has a first fluorescent layer 922 containingred phosphor material. The second fluorescent layer 921 may contain bothgreen phosphor and blue phosphor material.

In FIG. 19C, a LED device has a first fluorescent layer 932 containingred phosphor and green phosphor material. The second fluorescent layer931 contains blue phosphor material.

In the embodiments of FIG. 19A, FIG. 19B and FIG. 19C, the LED modulemay be an ultraviolet LED emitting light with frequency between 200 nmto 380 nm.

Please refer to FIG. 20A and FIG. 20B.

In FIG. 20A, a LED device has a LED module 751 surrounded by an invertedU shape first fluorescent layer 752 that is further surrounded by asecond fluorescent layer 753.

In FIG. 20B, a LED device has a LED module 761 surrounded by a domeshape first fluorescent layer 762 that is further surrounded by a secondfluorescent layer 763.

Please refer to FIG. 21A, which illustrates a COB LED device, with LEDchips 851 covered by a first fluorescent layer 853 and a secondfluorescent layer 852.

Please refer to FIG. 21B, which illustrates a CSP LED device, with a LEDdie 861 surrounded by a first fluorescent layer 863 and a secondfluorescent layer 862.

Please refer to FIG. 21C, which illustrates another CSP LED device, witha LED die 871 surrounded by a first fluorescent layer 872 and a secondfluorescent layer 873.

Please note that the different arrangement and shapes of the fluorescentlayers, which teaches persons of ordinary skilled in the art to performeven other variations, which should be still regarded as within theinventive scope.

Please refer to FIG. 22A, which illustrates a LED device with a stripsubstrate 953 having two surfaces covered by a fluorescent layers 951,952, 953 and 954.

Please refer to FIG. 22B, which illustrates a LED device with asubstrates 964 as a flexible circuit board substrate with fluorescentlayers 962 and 963 covered thereon.

The several embodiments mentioned above may be applied with desiredcombination of previously mentioned fluorescent layer features.

Please refer to FIG. 23A, FIG. 23B and FIG. 23C.

In addition to stack fluorescent layers, the fluorescent layers may beplaced in the same level.

In FIG. 23A, a packaging housing 651 defines two containers 6512 and6511 for containing two fluorescent layers mentioned above.

FIG. 23B further illustrates that the two containers 6611, 6612 may havedifferent size in response to different luminous output of differentcolors. Corresponding numbers of LED chips may be provided for suchdesign requirement, too.

FIG. 23C show an interleaved arrangement of different color fluorescentlayers. Other interleaved patterns may be used.

Please refer to FIG. 24, which illustrates a LED device having a firstfluorescent layer 681 and a second fluorescent layer 682. A separatingcomponent 683 is provided to prevent light from the second fluorescentlayer 682 to emit back to the first fluorescent layer 681.

Reflecting surfaces may even be provided to further optimize the overalloutput.

Please refer to FIG. 25, which illustrates a LED device with a packageside wall 691 having a tilt angle. In such design, light from the topfluorescent layer may have less chance to emit back to the bottomfluorescent layer, causing better luminous efficacy and CRI as mentionedabove.

In addition to the above-described embodiments, various modificationsmay be made, and as long as it is within the spirit of the sameinvention, the various designs that can be made by those skilled in theart are belong to the scope of the present invention.

The invention claimed is:
 1. A LED device, comprising: a LED modulecomprising a plurality of LED components mounted on a substrate foremitting an original light of an original spectrum; a first fluorescentlayer surrounding the plurality of LED components for converting theoriginal light to a first output light of a first spectrum; a secondfluorescent layer stacked on the first fluorescent layer for convertingthe original light not absorbed by the first fluorescent layer andentering the second fluorescent layer to generate a second output lightof a second spectrum, wherein the substrate is a transparent elongatedstrip, and wherein there is an intermediate part between the firstfluorescent layer and the second fluorescent layer, the intermediatepart comprising mixed materials of the first fluorescent layer and thesecond fluorescent layer, and the intermediate part has a plurality ofmicro convex structures between the first fluorescent layer and thesecond fluorescent layer.
 2. The LED device of claim 1, wherein thefirst fluorescent layer is a dome shape and the second fluorescent layerand the substrate surround the first fluorescent layer.
 3. The LEDdevice of claim 1, further comprising a package housing, wherein thepackage housing and the substrate form a container for storing the firstfluorescent layer.
 4. The LED device of claim 3, wherein the packagehousing has a surrounding side wall with larger peripheral size at topthan at bottom.
 5. The LED device of claim 3, wherein the packagehousing has a surrounding side wall with a reflecting surface facing tothe first fluorescent layer.
 6. The LED device of claim 1, wherein aheat dissipation material is mixed in the first fluorescent layer. 7.The LED device of claim 1, wherein the first fluorescent layer and thesecond fluorescent layer have phosphor material, and the phosphormaterial has larger density near bottom than top in the firstfluorescent layer and the second fluorescent layer.
 8. The LED device ofclaim 1, further comprising a package housing, wherein the packagehousing has a side wall with a convex structure engaging the firstfluorescent layer.
 9. The LED device of claim 1, further comprising apackage housing, wherein the package housing has a side wall with aconcave structure engaging the first fluorescent layer.
 10. The LEDdevice of claim 1, wherein the first fluorescent layer has a firstconvex surface on top of the first fluorescent layer, the secondfluorescent layer has a second convex surface on top of the secondfluorescent layer.
 11. The LED device of claim 10, wherein the firstconvex surface and the second convex surface forming lens guiding thefirst output light and the second output light for mixing the firstoutput light and the second output light.
 12. The LED device of claim 1,wherein the first fluorescent layer has a first concave surface on topof the first fluorescent layer, the second fluorescent layer has asecond concave surface on top of the second fluorescent layer.
 13. TheLED device of claim 1, wherein an intermediate surface between the firstfluorescent layer and the second fluorescent layer is a convex curvesurface.
 14. The LED device of claim 1, wherein an intermediate surfacebetween the first fluorescent layer and the second fluorescent layer isa concave curve surface.
 15. The LED device of claim 1, wherein thefirst output light, the second light and the original light not absorbedby the first fluorescent layer and the second fluorescent layer form anoverall output spectrum of a white light.
 16. The LED device of claim15, wherein the first fluorescent layer and the second fluorescent layerboth comprise red phosphor material for generating 640-650 nm outputlight.
 17. The LED device of claim 15, wherein the first fluorescentlayer and the second fluorescent layer both comprise red phosphormaterial for generating 628-635 nm output light.
 18. The LED device ofclaim 1, wherein the original spectrum is substantially corresponding toa ultraviolet light, the second fluorescent layer comprises greenphosphor material and blue phosphor material for generating a greenlight and a blue light, the first fluorescent layer comprises redphosphor material for generating a red light.
 19. The LED device ofclaim 1, further comprising a third fluorescent layer having bluephosphor material for generating blue light spectrum, wherein the secondfluorescent layer comprises green phosphor material for generating agreen light, and the first fluorescent layer comprises red phosphormaterial for generating a red light.
 20. The LED device of claim 1,wherein the first fluorescent layer comprises red phosphor material andgreen phosphor material for generating a red light and a green light andthe second fluorescent layer comprises blue phosphor material forgenerating a blue light.